Electric fuse.



C. W. DAVIS.

ELECTRIC FUSE.

APPLICATION FILED APR.22.1913.

1,152,148. Patented Aug. 31,1915.

} F|B-l'. 6 & 9- v 1" 9 Q Q 1 1 l 31- 7 30 e2 18 0 j I 5 "Wf'o- W M I 6% used to designate like parts.

U ITED": STATES PATENT OFFICE.

' CHARLES w. DAVIS, 0E EnGEwoRrn, rENNsYLvAmA, ASSIG1\IOB. To STANDARD UNDERGROUN CABLE COMPANY, or PITTSBURGH, PENNSYLVANIA, A con- PORATION OF PENNSYLVANIA.

ELECTRIC FUSE.

Patented Aug. 31, 1915.

Application filed April 22, 1913. Serial No. 762,887.

improvement the following is a specification.

electrlc cut outs My invention relates to and has or fuses for high voltage currents, particularly to ducting element nals and consists of a portion and adjoining extends between two term1- relatively low fusible high fusible portions. The objects of my invention are, first, to provide a simple and effective means for widening the gap between the high fusion portion of such conductors upon the blowing of the low fusion portion, and forsimultaneously breaking the circuit at a second point and secondly, to provide simple and effective means for relieving the tensile strain upon the low fusion portion of the conductor when a spring or other yielding means is employed for effecting a widening of the gap between the high fusion portions thereof.

In the accompanying drawing, which forms part of my specification, I have illustrated several embodiments of my invention.

Figure 1 of the drawing is a vertical sectional view of a junction box showing two entering cables and aremovable fuse structure, the casing .inclosing the fusible conductor being shown in longitudinal section; Fig. 2 is a longitudinal sectional View of another form of fuse illustrating a different embodiment of my invention; and Fig. 3 is a detached detail of construction.

In the several figures like numerals are features of the} The general structural complete fuse and its installation shown in i 1 the features of my invention,

Fig. 1 are similar to those illustrated and claimed in. my application, Serial No. 7 62,886, filed of'even date herewith. It will, however, -be readily apparent that my invention may be employed in various other forms and installations than that particularly shown and described herein.

Referring first, and briefly, to the general construction and installation in which my invention is illustrated and subsequently to the junction do with fuses wherein a 0011-.

box 1 is provided with two entering cables 2, to each of which is secured a terminal structure 3, comprising in part a spring-clip contact 4 and a' guide post 5. The removable fuse structure comprises a frame 6 of insulating material; conducting brackets 7 and 7*, secured to said frame, and having knife-blade contacts 30 at their lower ends; and, extending between said contacts, the fusible conductor, casing, etc., explained more fully hereinafter. As will readily be seen the frame 6 is provided with a handle 8 and with guide-ways 9, adapted to engage the guide posts 5, such an arrangement being particularly desirable when an arcdampening liquid fills the junction box, as in the present instance.

In Fig. 1 of the drawings, the casing 10, which is cylindrical and formed of a suitable insulating material, is secured. to the brackets 7 and 7 and has its open ends closed by means of closures 11 and 12, the latter of which fits loosely. The casing is provided with a partition 13; and the conductor c0m prising high fusion portions 14, 15 and a low fusion portion 16, extends through the casing, the high fusion portions 14; and 15 being secured to the closures 11 and 12, respectively. The outer ends of the conductor 14 is electrically connected by means of a flexible wire 17 to a binding screw 31 of the bracket 7; while the electrical connectlon befected. In my preferred construction to such an end, the closure 12 is provided with a contact cap 32, to which the conductor 15 is electrically secured, by a screw 33, and

-' which 1n turn is electrically connected to the bracket 7 by means of spring contact arms 34. It will be readily seen of this construction that the blowing of'the low fusion por tion 16 of the conductor will be effective to remove the closure 12 from the casing 10 and to carry with it the high fusion portion 15, and also that the circuit will be broken between the closure 12 and the bracket 7 The construction, illustrated in Fig. 2 of the drawings, is, as far as this'feature of my invention is concerned, the same as that illustrated in Fig.1, and just described. Means are alsoprovided for dampening or breaksmall physical strength.

quickly drawing out and quenching the arc which may have been established.

In Fig. 1 the partition 13, formed preferably of insulating material and having a small opening 18 through the center of it,

divides the casing 10 into an explosion chamber 19 and a retracting chamber 20. Tlie means for drawing the conductor 1t through the opening 18 and into the retracting chamber consist, in this instance, of a coil spring 21 formed of the conductor'Ll itself, which, in order to have good conduct-ing qualities and at the same time be sufliciently yielding, may be made of copper coated steel wire. It will be understood that, when such a conductor is thus coiled into a spring, the electromagnetic action of the current flowing through the conductor will materially increase its tension. In Fig. 2 the spring 21" is independent of the conductor 14", and. being preferablyformed of high resistance material, will receive little, if any, of the current carried by such conductor, and hence will exert less stress due to electromagnetic action.

Another feature of my invention has to do with means for relieving the low fusion portions of .fuse conductors from strains normally placed upon them by yielding elements such as the springs just described. In fuses for high voltage and low amperage currents. the fusible portion of the connecting conductors must, particularly when sur rounded by an arc-dampening liquid, be very small in cross-section and hence of 'hen, therefore. such fusible portion becomes heated. and its strength diminished accordingly, itis liable to rupture under the strain of a continu ously acting spring or like element before its rated current-carrying capacity has been reached. In order to eliminate this difliculty I providevmeans for relieving the tension upon the low fusion portion of the conductor, but in no way interfering with the action of the tension producing means to remove or withdraw the high fusion portion of the conductor after such low fusion por tion' has melted. The simplest means, which Iliave illustrated to this end, are shown in Fig. 2. wherein the ends of the high fusion portion 14" and 15" are mechanically connected' by means of a strip 35. which will carry little if any of the current flowing through the fuse strip, but which will be ruptured by the blowing of the low firision portion 16", which, it will be seen, wi 1 not be subjected to any tension when carrying a. current. The strip 35 may be made of non-conducting material such as glass fiber, or quarts fiber, or may be made of a low conducting, metal such as a fine steel wire, all of which materials will relieve the low fusion portion 16 of the tension placed upon the other parts of the conductors,'but-which will readily be fused or broken upon the fusion of said portion 16". Furthermore, it is characteristic of the materials mentioned that they are non-combustible, and hence upon their fusion-do not add materially to the volume of gases formed in the fuse casing by the explosion of the fuse. In Fig. 3 I have illustrated a similar means for reliev ing the tension from the low fusion portion of the conductor, wherein fusible or dis ruptable tension strips 35" and 35 are se- ".ured to the opposite ends of non-conducting arms 36 and 36*, respectively, which arms are in turn secured to the high fusion portions 15 and li The strips, or cords 35 and 35 are looped through each other, and each is connected to the opposite ends of a single arm, so that the high fusion portions will free to move when either of said strips is disrupted.

- In the construction shown in Fig. 1 a dis ruptable or fusible cord '25, indirectly relieves the tension upon the low fusion portion 16, such strip in this particular arrange ment extending transversely of and adjacent to said portion 16, and being connected at one end to the casing 10 and at the other end to one arm of a pivoted lever 24:. The opposite arm of said lever engages the arm 23' of an insulated bell-crank lever 22, 23, the arm :22 thereof engaging a. loop 39 formed in the high fusion portion 14: at the end of the spring 21. The arrangement is such that the cord 25 holds the lever :21 and bell-crank lever 2-2, 23 in the tension-relieving position shown in the drawing while 1 normal currents are flowing through the fu sible portion 16, but when the said portion 16 blows (by reason of an abnormal current) said cord 25 is disrupted or fused and re leases the lever 24, and hence the spring 21. In order to accelerate or make more certain the disruption or fusion of the tension cord 25, said cord may extend through a stopper or plug 26 adapted to close an opening 27 in the casing 10, the arrangement being such that the explosive force of the fusion Dortion 16 will act against the stopper 26 and expel it from the casing opening 27.

The operation of the fuse illustrated in Fig. 1- is as follows, assuming that the parts thereof are arranged in their normal operative position. as shown therein: 'hen the current carried from one cable conductor to the other through the fuse conductor 14, 16

and 15, exceeds a predetermined abnormal strength, the low-fusible portion 16 blows, the explosive force being effective to remove the closure 12 from the casing, and the arc momentarily formed being effective to rupbreaking of the circuit between such closure and the bracket 7 Upon the rupture of the wire 25, either through its fusion or through I the tension added to it by the explosive force acting upon the plug 26, the right hand end of the lever 24 will rise and release the bellcrank lever 22, 23 so that the spring 21 will be eflective to draw the free end of the conductor portion 14 through the partition 13 and 14 into retracting chamber 20, thereby dampening the arc and also widening the gap between the free conductor ends.

I claim as my invention:

1. In an electrical installation, the combination of a pair of electrical conductors, and an electric fuse closing a circuit between said conductors, said fuse comprising a casing having an opening therein, a removable closure forsaid opening, a contactor electrically secured to one of said conductors, a second contactor secured to said closure and adapted to contact with the first named contactor when said closure is in g the casing opening, a fuse strip comprising a low fusion portion and adjoining high fusion portions,

one of said high fusion portions being elec-' trically secured to the contactor attached to said closure, said closure being removable from said casing on and by the blowing of said low'fusion portion and by such movement simultaneously effective to widen the gap between the high fusion portions of said fuse strip and to release said contactors from engagement with each other.

2. In an electric fuse, the combination of a casing, a fuse strip within said casing comprising a low fusion portion and adjoining v high fustion portions, yielding means secured to a high fusion portion and effective to exert a pull thereon upon the blowing of the low fusion portion, and means including a fusible noncombustible cord for relieving said low fusion portion of the ull of said yielding means, saidco'rdb'eing usible upon and by the blowing of said low fusion portion.

3. In an electric fuse, the combination of a casing, a fuse strip within said casing comprising a low fusion portion and adjoining high fusion portions, yielding means secured to a high fusion portion and efiective to exert a pull thereon upon the blowing of the low fusion portion, and means including a fusible wire for relieving said low fusion portion of the pull of said yielding means, said wire being fusible upon and by the blowing of said low fusion portion.

l. In an electric fuse, the combination with a conductor comprising high and low fusion portions, of a spring secured to said high fusion portion and adapted upon the blowing of said low fusion portion to move said high fusion portion away from the zone of fusion, a pivoted finger effective in one position to withstand the strain of said spring and means for holding said finger in said position, said holding means being rendered ineffective for such purpose upon the blowing of said low fusion portion.

5. In an electric fuse, the combination with a casing, and a conductor comprising high and low fusion portions; of a spring exerting its tension on said conductor and adapted upon the blowing of said low-- fusion portion to move a free end of said high fusion portion away from the zone of.

' fusion, a'finger pivotally borne by said casing and adapted to engage said spring and withstand the tension thereof, and means for holding said finger in spring-engaging position, said finger-holding means being rendered ineffective upon the blowing of the low fusion portion of said conductor.

6; In an electric fuse, the combination of a casing, a partition dividing said casing into explosion and retracting chambers, a

.conductor extendingthrough said casing and partition and provided within said explosion chamber with a low fusion portion,

said conductor forming a coiled tension spring within said retracting chamber, a

finger pivoted to said casing and'engaging' said spring, and means including a ortion destructible upon the blowing of the use for holding said finger in spring-engaging po-.

sition.

In testimony whereof I have hereunto set my hand. a CHARLES W. DAVIS.

Witnesses:

PAUL N. CRrroHLow; FRANCIS J. TOMASSON. 

